Current methods of high-volume chip testing utilize complex, large and costly devices which are unreliable in testing some types of chips, most notably high-speed gallium arsenide devices. In addition, prior art probe heads typically probe only the outer perimeter of chips and are unable to test bonding pads located in the internal portion of chips undergoing test. An example of a commonly used fixed probe head for testing integrated circuits can be found in U.S. Pat. No. 4,563,640 to Hasegawa. This type of probe head fixture is typically mounted on an automated testing device which is used for high volume testing of integrated circuits before they are cut from a wafer. The testing procedure is for the probe head to be lowered onto the particular dye to be tested within the wafer, with the probe "fingers" lowered to contact the bonding pads to made electrical connections for testing. The fingers bring out the electrical paths to a test computer or similar machine which applies stimuli to the input pins and records responses on the output pins to determine whether the chip is good. After it has been determined whether the chip is good or bad, the probe head is raised and moved to a new location over another dye on the wafer to be tested. Process is repeated for each dye on the wafer until all of the chips have been tested.
The aforementioned probe heads of the prior art are designed to make electrical contact with a large number of bonding pads corresponding to a large number of I/0 pins and power pins. The manufacture and maintenance of such probe heads is expensive and the probe heads themselves are easily damaged. The probe lead wires from the test computer typically enter in a single planar surface and touch bonding pads that are located on the periphery of he chip to be tested. This design and location of the probe fingers makes for an extremely dense and large probe head since the probes are fixed in a conical radial array corresponding to the periphery of the chip. This radial design necessarily forces the outer diameter of the probe head with the connecting wires to be quite large. Thus, expansion of probe heads to handle a larger number of probe points and to have the ability to probe bonding pads within the internal portion of the chips becomes unwieldy.
The present invention overcomes the above-enumerated problems and other shortcomings associated with current chip testing devices.